Analysis showed that the frequency of the nine types of eccDNA in lung adenocarcinoma patients was higher than that in healthy controls, with four types of eccDNA (DOCK1, PPIC, TBC1D16, and RP11-370A5.1) were only expressed in patients with lung adenocarcinoma, thus indicating that this specific eccDNA exists in the plasma of patients with lung adenocarcinoma. Here, PPIC is linked to lung adenocarcinoma.